Study was conducted in conditions of strict long-term experiment, in a randomized block with four replications, on drained meadow located on mineral soil in Falenty. The aim of this study was to identify the circulation of magnesium and its balance in conditions of differentiated fertilization of irrigated meadows and without irrigation. Research treatments were: four levels of fertilization (N/60, N/120, N/180 and N/240) and two natural-mineral fertilization with the use of liquid manure (G/180, G/240) in conditions of optimal soil moisture that was irrigated and periodic shortages of water (without irrigation). In autumn 2008 and 2011 Mg content in soil and its pH were determined. During the years 2009-2011 three cuts of meadow sward were harvested and the yields of dry matter and macronutrient content were evaluated. The considerable variation in the distribution and amount of rainfalls during the growing season in period of study was observed. Significant differences in yielding between compared treatments were stated. Negative balances of magnesium on objects fertilized with mineral fertilizers were recorded. Liquid manure fertilization significantly implemented the deficiency of magnesium in the soil. In comparison with mineral fertilization liquid manure fertilization clearly improved the balance of this element. The balance was more beneficial for irrigated objects than for objects without irrigation. The soil richness in magnesium in both layers (0-10 and 10-20 cm) was significantly lower on objects without irrigation. It indicates on the Mg bringing with irrigation and leaching.